diabetic ketoacidosis. do not use levemir® if you are allergic to any of its ingredients. the most common side effect is low blood sugar, which may cause symptoms such as sweating, shakiness, confusion, and headache. severe low blood sugar can be serious and life threatening. ask your healthcare provider about alcohol use, operating machinery, or driving. other possible side effects include injection site reactions. tell your healthcare provider about all medicines you take and all of your medical conditions. get medical help right away if you experience serious allergic reactions, such as body rash, trouble with breathing, fast heartbeat, or sweating. with flexpen®... say good night to vial and syringe. ask your doctor about levemir® flexpen. covered by 90% of insurance plans, including medicare. find your co-pay at myflexpen.com.